Assistant professor Sarah Burke, PhD student Katherine Cochrane and Master’s student Tanya Roussy fine-tune equipment in UBC's Laboratory for Atomic Imaging Research. Photo: UBC.As the push for tinier and faster electronics continues, a new finding by University of British Columbia (UBC) scientists could help inform the design of the next generation of cheaper, more efficient devices. The work, published in Nature Communications, details how electronic properties at the edges of organic molecular systems differ from the rest of the material.
Organic semiconductors are of great interest for use in solar panels, light emitting diodes and transistors. They're low-cost, light and take less energy to produce than silicon semiconductors. Interfaces – where one type of material meets another – play a key role in the functionality of all these devices.
“We found that the polarization-induced energy level shifts from the edge of these materials to the interior are significant, and can't be neglected when designing components,” says UBC PhD researcher Katherine Cochrane, lead author of the paper.
“While we were expecting some differences, we were surprised by the size of the effect and that it occurred on the scale of a single molecule,” adds UBC researcher Sarah Burke, an expert on nanoscale electronic and optoelectronic materials and an author on the paper.
The researchers used scanning tunneling spectroscopy to study ‘nano-islands’ made up of molecular clusters of an organic semiconductor; these clusters were deposited on a silver crystal coated with a layer of salt just two atoms deep. The salt layer acts as an insulator and prevents electrons in the organic molecules from interacting with those in the silver, allowing the researchers to isolate interactions between the organic molecules in the nano-islands.
This revealed that not only did the molecules at the edge of the nano-islands have very different properties than those in the middle, the variation in properties depended on the position and orientation of other molecules nearby. The researchers, part of UBC’s Quantum Matter Institute, used a simple, analytical model to explain the differences; this model can be extended to predict interface properties in much more complex systems, like those encountered in a real device.
“Herbert Kroemer said in his Nobel Lecture that ‘The interface is the device’ and it’s equally true for organic materials,” says Burke. “The differences we’ve seen at the edges of molecular clusters highlights one effect that we’ll need to consider as we design new materials for these devices, but likely they are many more surprises waiting to be discovered.”
Cochrane and her colleagues plan to keep investigating what happens at the interfaces of these materials and to work with materials chemists to guide the development of design rules for the structural and electronic properties of future devices.
This story is adapted from material from the University of British Columbia, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.